Safety device for gasoline burners



Dec. 3, 1963 J- M. DUNSTON SAFETY DEVICE FOR GASOLINE BURNERS 2 Sheets-Sheet 1 Filed Jan. 28, 1953 VIZ ' INVENTOR. JAMES M. DUN5TON 3, 1963 J. M. DUNSTON SAFETY DEVICE FOR GASOLINE BURNERS 2 Sheets-Sheet 2 Filed Jan. 28, 1953 INVENTOR. J/IMEE) M. DUNSTON 1104M f/ M114 .1.

United States Patent SAFETY DEVICE F03 GASULINE BUFNEES James M. Dunstan, Naticlr, Mass, assignor to the United States of America as represented by the Secretary of the Army Filed Jan. 23, 1963, Ser. No. 254,516 7 Claims. ({Il. 15842.4) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein, if patented, may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to a safety device for liquid fuel burners, particularly, gasoline burners, to prevent excessive pressure buildup in the fuel tanks thereof and to minimize the possibility of explosion.

in outdoor camping activities and military field operations, pressurized liquid fuel burners are often used for heating and cooking purposes. Such burners range in size from very compact stoves having a capacity of about 2,500 l3.t.u. per hour for use by individuals or small groups to relatively large and complex burner units used by the military in cooking and baking for large groups, such as the Burner Unit, Gasoline Field Range Outfit described in Military Specification MIL-B-40098 (QMC) dated 24 December 1959, which has a capacity of about 55,000 B.t.u. per hour. All of these burners have certain common characteristics including a closed fuel tank or reservoir, means for creating a pressure greater than atmospheric within the tank and a fuel filling device which prevents complete filling of the tank. The latter device insures a minimum vapor space above the level of the liquid fuel in the tank at all times. This vapor space provides for safe expansion of the fuel under normal operating conditions as the temperature of the fuel rises due to the proximity of the burner where combustion is occurring. When the unit is operating, fuel is drawn from the lower portion of the tank through a fuel feed tube to a generator or vaporizer wherein the liquid fuel is converted to vapor prior to being fed to the burner in order to provide for more efficient combustion. Because of the requirement for portability of such equipment, the fuel tanks, the generator and the burner are usually arranged in close proximity to one another to provide a compact unit. In this arrangement, considerable heat is refiected or radiated from the burner and the container being heated above the burner and heat is conducted from the generator and other parts of the unit to the fuel tanks. The resulting increase in the temperature of the liquid fuel and fuel vapors in the tank causes an increase in the pressure within the tank. When a burner unit is used at or near its heating capacity for heating a large container and and to an even greater extent when the unit is used within afield range cabinet or field oven, the danger of ex cessive pressure buildup in the tanks with the possibility of explosion is a recognized problem. Close surveillance of the burner may permit corrective action by reducing the rate of combustion in the burner. However, such surveillance is not always possible in actual operation since distraction or, in the case of military operations, operating conditions may not permit close attention.

It is therefore an object of the present invention to provide a means for the prevention of explosions of fuel tanks in gasoline fired field range burner units.

Another object of the invention is to provide a safety device which will automatically cut oil the supply of liquid fuel from a fuel tank to a burner unit in a gasoline field range when the temperature in the fuel tank reaches a predetermined level.

A further object of the invention is to provide a safety device which will automatically reduce the pressure with 3,ll2,788 Patented Dec. 3, 1963 in the fuel tank of a pressurized gasoline burner by discharging combustible vapors from within the tank through the burner for normal combustion,

A still further object of this invention is to provide a safety device for pressurized gasoline burners which is tamper-proof in that it cannot be by-passed or rendered inoperative.

A still further object of this invention is to provide a safety device which may be simply and inexpensively replaced after it functions.

A still further object is to provide a simple and inexpensive safety device which may be added to existing equipment without requiring any significant modification thereto.

Various other objects and advantages derived from the invention will be apparent from the following description of one embodiment of the invention and from the appended claims.

The foregoing objects are accomplished by providing a fuel feed tube having upper and lower portions joined above the level of liquid fuel in the tank by a fusible link. The material of which the fusible link is made is selected so that it will soften at a predetermined temperature to cause the lower portion of the fuel feed tube to separate from the upper portion thereof. The supply of liquid fuel to the generator is thus cut off and the fuel rich vapors in the upper part of the fuel tank are passed through the generator to the burner where they are safely consumed. It is to be understood that the fusible section of the fuel feed tube will be made of a material which will permit continuous operations of the burner under normal safe conditions but will fail due to melting or loss of strength when the temperature within the fuel tank rises to a' level at which continued operation will produce an excessive pressure build-up within the tank.

The present invention may be more fully understood by reference to the accompanying drawings showing one embodiment of the invention, wherein like reference characters designate like parts in the various views, and in which:

FIGURE 1 is a top plan View of a gasoline field range burner unit similar to that of the above-mentioned Military Specification, but omitting some of the elements which are not essential to an understanding of the in vention;

FIGURE 2 is a partial vertical section along the line 2-2 of FIGURE 1, showing the fuel feed tube in its normal operating condition; and

FlGURE 3 is a partial vertical section along the line 3-3 of FIGURE 2 showing the fuel feed tube in the fail-safe condition following melting of the fusible section.

Referring more particularly to FIGURES 1 and. 2 of the drawings, the burner unit comprises generally a tubular frame 4, a tank assembly 5, support members 6 joining the tank assembly to the frame, a fuel feed tube assembly 7, a generator assembly 8, a control valve 9 and burner head 1th In addition, such units are generally provided with pro-heater means, an air pump and air valve, heat shields arranged between the burner and the fuel tank assembly and a pressure indicating gage, all of which have been omitted from the drawings for purposes of clarity. The generator extends over the burner such that the heat from the flame at the burner serves to vaporize the liquid fuel passing through the generator prior to its being introduced to the burner.

The tank assembly 5 comprises two tanks 11 and 12 inter-connected by top and bottom rear straddle tubes 13 and 14 and a top front straddle tube 15 creating a unitary fuel reservoir. The top and bottom rear straddle tubes 13 and 14 are connected midway between the tanks by a vertical connecting tube 16. A threaded bushing 17 having a central bore 13 therethrough is mounted on the top of the top rear straddle tube 13 such that the central bore thereof is register with the central bore of the vertical connecting tube 16. The top of bushing 17 is provided with an inverted frusto-conical surface 19 for a purpose to be described.

The fuel feed tube assembly 7 is comprised of a lower tube portion 20, a fusible link 21 and an upper tube portion 22 having a flange 23 fixed to its upper end. The lower and upper tube portions 20 and 22 are connected by the fusible link 21 by threaded joints or by other conventional means. The fuel feed tube assembly is sized to permit insertion thereof through the central bore 18 of the bushing 17 and the vertical connecting tube 16 until the undersurface of the flange 23 seats on the frustoconical surface 19 of the bushing. The length of the assembly is such that when the flange is so seated the lower end of the tube will extend almost to the bottom of the bottom rear straddle tube 14. The diameter of the tube portions 20 and Z2 and fusible link 21 are selected to permit clearance within the vertical connecting tube 16 and the central bore 13 of bushing 17 at all times; while the length of the upper tube portion 22 is such that the lower end thereof will always be above the level of liquid fuel in the reservoir upon separation of the upper and lower tube portions 22 and 21 by failure of the fusible link 21.

The generator assembly 8 is comprised of an enlarged elongated tubular member 24 which is preferably filled with chopped steel wool fiber which serves as both a heat transfer and filtering medium, whereby the liquid fuel passing through the generator is vaporized and some fuel additives, particularly tetraethyl lead, are filtered out. The front end of the generator is provided with a downwardly extending tube (not shown) which connects the generator to the control valve 9. The rear end of the generator is provided with a downwardly extending tube 25 including a flanged lower end portion 26 which cooperates with nut 27 to attach the generator assembly to the fuel feed tube assembly 7 and the tank assembly at bushing 17. The flanged end of tube 25 is preferably provided with a spherical surface 28 to assure a pressure-tight joint with upper surface of flange 23 of the fuel feed tube assembly 7.

In the operation of the burner unit described, the tanks are filled with gasoline to the level permitted by the filling device (not shown). The filling opening and the control valve 9 are then closed. The tanks are pressurized by means of an air pump (not shown). The front portion of the generator is heated by the pre-heating means (not shown) which also may serve as a pilot for igniting the main burner when the control valve 9 is opened. The control valve 9 is used to establish the desired rate of combustion at the burner. The heat radiated and conducted from the burner to the fuel tanks 11 and 12 will normally cause suflicient pressure build-up in the tanks to maintain operating pressure as the level of fuel in the tanks diminishes during operation. Should the unit be operated within the confines of a field range cabinet or field oven or the like or under other conditions whereby the temperature increase in the tank reaches a point where excessive pressures will occur, the fusible link 21 softens and the weight of the lower portion 20 of the fuel feed tube 7 causes the link to separate. The separation of the upper and lower portions 22 and 20 of the fuel feed tube cuts off the supply of liquid fuel to the generator and permits the fuel vapors under pressure in the upper portion of the tanks to pass through the generator and the control valve to the burner where they are consumed. The combustion of these vapors is accomplished in a very short time and the flame at the burner rapidly diminishes until it is extinguished through a lack of suificient fuel. The pressure within the tanks at this point has been reduced to atmospheric pressure and the dangerous condition relieved.

The fusible link 21 may be made of any solid having sufiicient strength under normal safe operating conditions to support the weight of the lower fuel feed tube and having a melting point sufficiently low to allow it to melt and prevent further flow of liquid fuel to the generator when pressure in the fuel tanks reaches a dangerous level. The limit of safe operating conditions will depend on the materials of construction, thickness, strength of joints, etc. of the fuel tanks and fuel feed tube assembly. However, for such burner units as that covered by the above-mentioncd military specification, a fusible link which melt between 350 and 400 degrees F. will be acceptable. Numerous alloys are suitable for this purpose. Tin-lead solders are especially useful because of their low cost. A 60-40 (by weight) tin-lead solder is liquid at 374 'F., solid at 361 F., and pasty between these temperature. A 70-30 (by weight) tin-lead solder is liquid at 378 F., solid at 361 F, and pasty between these temperatures. A 91-9 (by weight) tin-zinc solder melts sharply at 390 F. The above-mentioned solders will work satisfactorily in the fusible link of this invention. Other solders which are available and will work within the above-mentioned preferred range, or at lower or higher temperatures, if desired, are described in Soldering Manual, published by the American Welding Society, 33 West 39th Street, New York 18, New York (1959). It is to be understood, however, that pure metals, such as lead, tin, zinc, indium, and others may be used in the fusible link if conditions indicate that the melting points of such metals meet the requirements for a fail-safe device such as has been described above. Similarly, it is to be understood that thermoplastic organic polymeric materials may be used in the fusible link and will be selected according to their melting points, their strengths under normal safe operating conditions, and their resistance to gasoline and other fuels which might be used in burner units containing fusible links in the fuel feed tubes, Cellulose esters, such as cellulose acetate butyrate, cellulose propionate, and cellulose acetate, are particularly suitable for this purpose.

In order to restore normal operation of the burner unit after failure of the fusible link, the nut 27 is disengaged from the bushing 17, the generator assembly 8 is moved away from the bushing, the separated upper and lower fuel feed tubes are removed, and a new fuel feed tube assembly is installed. The generator is restored to its operational position and nut 27 is tightened. The unit is then ready for operation. Various devices may be used to remove the separated portions of the fuel feed tube assembly. The top portion 22 may be easily removed by grasping the flange 23 which is exposed when the generator is removed from bushing 17. A wire or rod having one end bent to form a small hook may be inserted through the bushing and manipulated so that the hook engages the lower edge of the lower portion 20 such that it may be withdrawn through the bushing 17. A magnet attached to a rod may also be used for removal of the separated lower portion if the latter is constructed of a magnetic responsive material.

While the present invention is particularly useful in conjunction with the gasoline fired field range burner units herein described, it can also be used as a safety device in other types of burners or heaters employing liquid fuels, such as gasoline, kerosene, or other volatile fuels, whenever there is a possibility of an excessive build-up of temperature and pressure of fuel vapors in the fuel tanks of such equipment as the result of heat being reflected radiated, or conducted back to the fuel tanks and fuel feed tubes from the burner or generator or objects being heated. Generally, the invention may be incorporated in existing equipment by merely replacing the existing fuel feed tube with a new fuel feed tube embodying a fusible link in accordance with the invention without further modification to the equipment.

It will be understood that various changes in the details,

materials of construction, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art Within the principle and scope of the invention as expressed in the appended claims.

I claim:

1. A safety device for a liquid fuel burning apparatus having a reservoir capable of being filled with liquid fuel under pressure up to a predetermined level providing a vapor space above said liquid fuel in said reservoir comprising a fuel feed tube for conducting liquid fuel from said reservoir to the burner portion of said apparatus, said fuel feed tube comprising upper and lower tube portions joined at a point within said reservoir and above the said predetermined maximum level of liquid fuel therein by thermally actuated separable means whereby said upper and lower tube portions are separated upon the occurrence 4 4. A safety device as in claim 1 wherein said thermally actuated separable means is a link fusible at a temperature of from about 350 F. to about 400 F.

5. A'safety device for a liquid fuel burner having a reservoir capable of being filled with liquid fuel under pressure up to a predetermined level providing a vapor space above said liquid fuel in said reservoir comprising a fuel feed tube removably mounted in said reservoir, said fuel feed tube being comprised of upper and lower tube portions joined at a point within said vapor space by thermally actuated separable means whereby said lower tube portion is separated from said upper tube portion at the occurrence of a predetermined temperature cutting off the flow of liquid fuel from said reservoir.

6. A safety device as in claim 5 wherein said thermally actuated separable means is a link fusible at said predetermined temperature.

7. A safety device as in claim 5 wherein said thermally actuated separable means is a metal alloy link fusible at a temperature of from about 350 F. to about 400 F.

References Cited in the tile of this patent UNITED STATES PATENTS 888,488 Gurley May 26, 1908 1,609,134 Sladky et al Nov. 30, 1926 2,812,017 Vant Nov. 5, 1957 

1. A SAFETY DEVICE FOR A LIQUID FUEL BURNING APPARATUS HAVING A RESERVOIR CAPABLE OF BEING FILLED WITH LIQUID FUEL UNDER PRESSURE UP TO A PREDETERMINED LEVEL PROVIDING A VAPOR SPACE ABOVE SAID LIQUID FUEL IN SAID RESERVOIR COMPRISING A FUEL FEED TUBE FOR CONDUCTING LIQUID FUEL FROM SAID RESERVOIR TO THE BURNER PORTION OF SAID APPARATUS, SAID FUEL FEED TUBE COMPRISING UPPER AND LOWER TUBE PORTIONS JOINED AT A POINT WITHIN SAID RESERVOIR AND ABOVE THE SAID PREDETERMINED MAXIMUM LEVEL OF LIQUID FUEL THEREIN BY THERMALLY ACTUATED SEPARABLE MEANS WHEREBY SAID UPPER AND LOWER TUBE PORTIONS ARE SEPARATED UPON THE OCCURRENCE OF A PREDETERMINED TEMPERATURE CUTTING OFF THE FLOW OF LIQUID FUEL TO SAID BURNER PORTION AND PERMITTING THE FLOW OF VAPOR FROM SAID VAPOR SPACE TO SAID BURNER PORTION. 